Propulsive wing with inflatable armature

ABSTRACT

A very light wing, configured like a spherical segment, is intended to be used in the traction and lift of various loads. The wing includes a leading edge and a trailing edge and an inflatable armature covered by a flexible envelope. The surfaces of the wing are configured in the shape of an aircraft wing profile and the edges of the wing curve in two planes. The leading and trailing edges of the wing are oriented to intersect near the tips of the wing, and each of the tips of the wing receives a control rope via an adjusting plate. The control rope is passed through a pulley mounted on a craft to be displaced by a person through a harness. The wing can be used in sliding sports, yachting and gliding.

This invention concerns a propulsive wing of thick profile linked bycontrol ropes to the load to be pulled and including a inflatablearmature as well as a thin and flexible envelope.

There is a new generation of sails (still at the experimental stage)usable in the form of kites, that is to say linked to the loadexclusively by the control ropes, with these generally being limited innumber. These sails have numerous theoretical advantages: they relievethe strain on the sail-boat instead of forcing down its edge under thewind (supporting effect), they have an excellent efficiency ratiobecause they are not subjected to the disturbing influence of the wind,they are able to take advantage of the stronger and more regular windsfound at a higher altitude, and above all they have an irreversibleprofile in that they can pivot so that they always present the sameedge. And yet, in practice, it is clear that such sails are confrontedwith new problems which limit their efficacity: superimposed kitesystems, in a chain formation, pose great difficulties of deploymentduring launching, which has to take place, of necessity, on land. Some,because they are deployed on a rigid armature, are relatively heavy anddifficult to manage. Others, whether or not they are inflatable, canonly be maintained in position by a complex system of wires, whose useis delicate and constraining. Moreover, these sails for the most parthave a mediocre aerodynamic profile because they are subject tosecondary requirements which are often highly complex.

The propulsive wing described in this invention, because of its refinedshape, provides a solution to these difficulties. In fact, this wing,which is configured like a spherical gore, enables, thanks to theminimum strain it imposes on the structure, the use of an inflatablearmature. This armature contains compressed air and is designed andcalculated to integrate itself perfectly with the shape of the wing,without interfering with air-flow. It has a leading strut of a clearlysemi-circular shape and several struts which are transverse to theformer. It is enveloped in a resistant, light-weight material arragnedin such a way as to give it an aircraft wing profile of maximumefficiency. This wing is therefore of great lightness and very reduceddimension, once deflated and folded. Each end of the wing takes a longcontrol rope fixed to the load to be pulled, thus enabling the wing tocontrolled and directed. In order to adapt the wing to the differentwind strengths, it is possible to reduce the sail surface by removingthe rear part of the material by some appropriate method, such as a zipfastener.

Finally, both by the considerable buoyancy provided by the armature andby the simplicity of the control system, take-off even on water beingextremely easy to effect, this wing can be controlled by a user mountedon one or two skates or shoes, using a pulley attached to this harnessand through which is passed a single control rope linked to the two endsof the gore.

The propulsive wing is described in detail in the annexed drawings,provided as examples and on which:

FIG. 1 shows, in perspective, the wing according to the invention,

FIG. 2 shows, in section, the wing profile,

FIG. 3 shows, edge on, the wing according to the invention,

FIG. 4 shows, in perspective, the inflatable armature,

FIG. 5 shows, in section, a variation of the profile with a system forreducing the sail,

FIG. 6 shows, in profile, the wing according to the invention,

FIG. 7, 8 and 9 show the three stages of the graphic method of tracingthe sail pieces.

FIG. 10 shows the most sporting use in a nautical context.

The wing is always shown inflated by the wind. Its size can varyenormously according to the use, from less than half a sqaure meter in achild's toy to several dozens or even hundreds of square meters forheavy loads. The shape of the profile can also vary.

FIG. 1 gives an overall view of the wing. This is in the form of aspherical gore comprizing a leading edge (1) and a trailing edge (2) andis embodied by an inflatable armature (3 and 4) covered by a flexibleenvelope (5) both in the intrados (I) and in the extrados (S). Each ofits tips (6) receives through an adjusting plate (7) a control rope (8)linked to the load.

This wing functions aerodynamically speaking as an aircraft wing as FIG.2 shows, that is, it attacks the wind with a small angle of incidence(i) creating a pressure on the intrados side and a depression on theextrados side (S), the wind moving from the leading edge (1) towards thetrailing edge (2). The essential difference to an aircraft wing is thatthe former is a flat surface seen edge on and the wing in accordancewith the invention is clearly semi-circular, as shown in FIG. 3. Themain advantage of this shape lies in the fact that it imposes a minimumof strain on the armature. Moreover, the shape is self-sufficient, thatis, it needs no auxiliary structure. in fact the surface can be brokendown diagrammatically into three parts: a central part which developsthe propulsive force (P) (the wing properly speaking), and twoend-pieces. These latter represent about a third of the total surfaceand have three functions:

They act as control surfaces, that is they give longtitudinal stabilityto the wing.

They generate a force (T) which holds the tips apart and thus holds thestructure deployed.

They act as end-plates for the propulsive part (P) of the wing, that is,they limit the loss of pressure on the intrados to a minimum andtherefore the filling out of the depression on the extrados (S) (aproblem with standard sails). For this reason they can be called dynamiccontrol surfaces.

But no sail can present a small angle of incidence to the wind if it isnot maintained on the desired shape by an appropriate armature. Thearmature of the propulsive wing shown in FIG. 4 is inflatable, using aninflatable boat pump, for example, through one or several orifices (9),provided with stoppers and (secondarily) non-return valves. The pressurerequired is relatively weak and air can be replaced by a lighter gas tofacilitate flight in weak wind conditions. The struts are of roundsection and their shape is calculated for maximum integration into theprofile. They can be made in two ways: either as a duct plus an airchamber, or as an inextendable air chamber alone. The material must beflexible and stand up in suitable fashion to the pressure and torepeated foldings. Finally, the struts can be linked together, requiringonly one inflating orifice, or separated, in which case several orificesare required.

The leading strut (3) is equal in length to the leading edge. Itsdiameter (d) (FIG. 2) is proportional to the length of the profile (1)and this at all points on the sail. This strut therefore becomes thinnertowards its end to finish in a tip, which gives it, seen edge on, theshape of a crescent (FIG. 3). Its role is to prevent the leading edge(1) from moving away and the whole wing from becoming deformed,something which would greatly disturb flight control.

The transverse struts (4) have a length equal to the length of theprofile at the position where they are placed less the thickness of theleading strut against which they abut. Their number varies in relationto the size of the wing, and the thickness and flexibility of thefabric. Taking the example of a surface of 4 m2 and fabric of 100 gr/m2, there would be three struts regularly spaced. Their role is to preventthe fabric from creasing and they therefore work above all incompression.

As shown in FIG. 2, this armature bears an envelope (5) made of aflexible, light fabric made from a synthetic material or plasticsheeting, which does not lose its shape easily or absorb water and is asresistant as possible to wear and tear. This envelope totally surroundsthe armature, hiding it completely. The envelope and the armature arefixed together at their points of contact. A layer of fabric covers theupper side of the armature and forms the extrados (S) while anotherlayer covers the underside, forming the intrados (I). They meet at theback and are fixed togther.

In a different version (shown in FIGS. 5 and 6) one can use the samewing to provide two sail surface sizes, depending on the strength of thewind. To achieve this, it is necessary to fix a zip fastening (10)lengthwise across the sail, generally across the rear third of thesurface, in order to obtain a narrower wing if needed. As an example, awing of 6 m2 can be reduced to 4 m2. This can be a very practicalsolution on condition that the intrados envelope is fixed at the levelof the zip fastening, or removed (although the latter can slightlyreduce wing performance). Again it is necessary to ensure at the profiledesign stage that the reduction in sail surface will not affect theequilibrium of the sail. Finally, to obtain the best flight performance,the wing must have a wing length/maximum profile length ratio higherthan 2, the length of the wing being the length of the envelope (2)between the two tips.

As the wing is held at the two tips, it is in a position of stableequilibrium in flight when its angle of incidence in relation to thewind (i) provides a laminar air-flow round the profile. The angle (i)must be very small to enable the right direction or angle of lift inrelation to the wind. To achieve this result, the tips (O) (FIG. 7) mustbe an extension of the force (R) resulting from the push and dragforces, (R) being located at 42% of the length of the profile. Thispercentage can vary by a small amount depending on the shape of theprofile. As the wing surface is curved in both directions, and thereforenot expandable, and this percentage having also to be respected, itbecomes impossible to manufacture a wing of perfect shape according toold-fashioned methods. It is for this reason that a method using graphicprojection (see FIGS. 7, 8 and 9) has been developed, making it possibleto ascertain the exact shape of the sail-pieces or pieces of fabricwhich, assembled according to a radial disposition, form the envelope.Using this method the shape of the profile can be respected at allpoints on the wing.

On FIG. 7, the thick line represents the wing seen from the side. Thenumber of pieces and the shape of the profile have been chosenarbritarily. Let (O) be one of the tips of the sail, (AA') the axisdelimiting the front of the profile and parallel to (OO'), (AE) thelength of the profile. The surface (OA'B) represents the leading strut,(OBC) , (OCD) and (ODE) being the sail pieces. The point (O'), theorthogonal projection of (O) on the straight line (AE) is such thatAO'=42% of (AE). The projection is carried out from the imaginary point(X) located on the straight line (O'O) such that O'X >/ OO'.

FIG. 8, traced from FIG. 7, is a section of the chosen profile (only theextrados in this demonstration). Three straight lines (BC), (CD) and(DE) are traced, representing the profile obtained after assembly of thesail pieces (the more numerous the pieces, the closer the profileobtained is to the one intended). A perpendicular is projected from thepoint (X) to each of the straight lines. One obtains the intersectionpoints (X1), (X2) and (X3).

FIG. 9, taken from FIG. 8, but shown here at 1/2 scale, gives the exactshape of the sail-pieces. The three straight lines (BC), (CD) and (DE)are reproduced horizontally with the points (x1), (x2) and (x3).Verticals are traced to these points which stop at the tips (O) of thewing. For each piece one traces two arcs from the tips (O) and passingthrough points (B), (C), (D) and (E). In this example, (C) beingintegral with (x1), one obtains a straight line behind the first piece.The pieces are assembled in accordance with the arrows, edge againstedge, in such a way that the tips (O) join at the same point, byglueing, sewing or any other appropriate means. They are then fixed tothe armature. This method of manufacture using assembled pieces requiresfew facilities for artisanal production. However other methods ofmanufacture are envisagable in an industrial context, for exampleheat-forming of flexible sheeting on a wing-shaped mould, using variousmaterials.

Moreover, in order to enable a precise adjustment of the angle ofincidence (i), each tip can be provided with an adjusting plate (7)pierced with several holes, to which is fixed the control rope. If thisis attached towards the rear of the plate, the angle (i) becomes large,and if it is attached towards the front, (i) becomes small. The angle(i) hardly varies with the wind, except where the wind is weak, when theweight of the wing influences its behavior.

The control rope (8) must be light, resistant and stretch the leastpossible. Its length does not depend on any particular requirements.However, it should be borne in mind that while the wind is stronger andmore regular at a certain altitude, the weight of the control rope andits wind take-up may interfere with control of the wing. This is why alength of several dozen meters for wings of less than 10 to 20 m2 seemssuitable for kite use.

When the load to be pulled is a machine or device, the wing is linked toit by a single control rope passing through one or several pulleys.

When the load to be pulled is the user mounted on a small-sized machine,the control rope (8) is used as shown in FIG. 10 to adjust the wing inthe desired direction. Each of its ends is connected to one of the tips(6) of the wing. It passes through a swivel block (11) which turnsfreely on itself, fixed to a harness (12) worn by the user. Thepropulsive force provided by the wing acts on the control rope (8) ofthe pulley (11) then on the user, but the latter can control theapparatus by only slight effort, because the tensions on the controlrope are always equal on both sides of the pulley. The swivel blockenables the pulley (11) to turn on itself in order to eliminate twistsin the control rope (caused notably by take-off manoeuvers).

Using this insubmersible wing and its control system, take-off overwater is extremely easy and requires no external assistance. In its mostsporting application in a nautical context, the user is equipped withone or two special skates or shoes (13).

In a flight application, a person suspended from the wing by means of anappropriate harness, uses the same control system as described above(FIG. 10).

This wing can be used for traction or support of a person, a load, adevice or machine on water, on the ground (snow, ice, grass, sand, etc)or in the air. Among its numerous possible applications the most obviousconcern sliding sports, yachting, and sail-flight.

We claim:
 1. In a propulsive wing of an aerodynamic profile linked bycontrol ropes to a load, the wing including a thin flexible envelope andhaving a top surface and a bottom surface and an inflatable armaturemade up of a first strut and second struts, the first strut extendingalong a leading edge of the wing and having a thickness dimension thatvaries according to location along the wing leading edge whereby thefirst sturt has a thickness at its extremities that is less than thethickness of the first sturt near the middle section thereof, the winghaving a tailing edge, the first strut extremities forming tips, theimprovement in combination therewith comprising:the leading and trailingedges of the wing being oriented to intersect each other near the firststrut tips and the wing having an arcuate shape between the tips to forma lune-like spehrical segment which curves in two planes from one of thetips through the middle section of the first sturt to the other of thetips with each tip being adapted to receive a control rope with only twocontrol ropes being required by the wing, the improvement furthercomprising the variation of the first strut thickness dimension defininga crescent shape for the wing dimension between the top and the bottomsurfaces of that wing.
 2. The propulsive wing as defined in claim 1,wherein the improvement further comprises forming the exact shape ofvarious pieces of the wing using a graphic method of orthogonalprojection from a given point towards a required profile segment, andarranging the pieces thus formed according to a radial position to formthe envelope.
 3. The propulsive wing according to claim 1, wherein theimprovement further comprises a zip fastener for coupling a rear part ofthe envelope to a removable part.
 4. The propulsive wing according toclaim 1, wherein the improvement further comprises connecting each endof the control rope to one of said tips, and further including a swivelblock on the control rope and a harness adapted to be fixed to a userand adapted to be connected to said swivel block.